1. Field of the Invention
The present invention relates to a head suspension for supporting a magnetic head slider in a magnetic disk drive. In particular, the present invention relates to a piezoelectric actuator having a piezoelectric element that deforms in response to an applied voltage, to minutely move the magnetic head slider in a widthwise direction of the head suspension.
2. Description of Related Art
Small-sized, precision information devices are rapidly advancing and needs for micro-actuators capable of conducting positioning control for very small distances are increasing. Such micro-actuators are highly needed by, for example, optical systems for correcting focuses and inclination angles, ink jet printers for controlling ink heads, and magnetic disk drives for controlling magnetic heads.
The magnetic disk drives have an urgent issue to solve, i.e., increasing storage capacity. The storage capacity of a magnetic disk drive usually increases if the storage capacity of each magnetic disk contained in the magnetic disk drive increases. The storage capacity or recording density of a magnetic disk will increase, without changing the diameter thereof, if the number of tracks per inch (TPI) on the magnetic disk increases. For this, the width of each track on the magnetic disk must be narrow. To handle such narrow tracks on the magnetic disk, a magnetic head of a head suspension installed in the magnetic disk drive must conduct a precise positioning operation in a direction across the tracks. For realizing the precise positioning operation, there is a need of an actuator capable of accurately moving and positioning the magnetic head in a very small area.
To meet the need, the applicant of the present invention has proposed in Japanese Unexamined Patent Application Publication No. 2002-184140 a head suspension for a disk drive, including a base plate, a connection plate having a hinge thinner than the base plate, a load beam provided with a flexure and a magnetic head, and a pair of piezoelectric elements.
This related art employs a dual actuator system that involves, for a positioning purpose, a voice coil motor and the piezoelectric elements made of PZT (lead zirconate titanate).
The piezoelectric elements minutely drive a front end of the load beam in a widthwise direction (sway direction) of the head suspension. Compared with a single actuator system employing only a voice coil motor, the dual actuator system employing the voice coil motor and piezoelectric elements more precisely positions the magnetic head attached to the front end of the head suspension.
An important issue for the head suspension employing the dual actuator system is how to supply electricity to the piezoelectric elements.
A technique to approach this issue is disclosed in Japanese Unexamined Patent Application Publication No. 2003-61371 (in particular, FIGS. 9 and 10 thereof). This related art arranges a pair of wires on a head suspension. One of the wires is connected through wire bonding to a base electrode and the other wire is connected through wire bonding to an exposed part of the top face of each piezoelectric element.
This related art has a risk of cracking the piezoelectric element because the wire bonding process applies a local stress on the piezoelectric element to secure a bonding strength. If the wire bonding process is carried out with a reduced force not to crack the piezoelectric element, the bonding strength will be insufficient to deteriorate the reliability of electric connection to the piezoelectric element. It is very difficult to carry out the wire bonding process on piezoelectric elements to satisfy both the productivity and reliability of the piezoelectric elements.